Author: Zhang, Yuhang
Title: Wireless power transfer via iPad
Advisors: Wong, S. C. (EIE)
Degree: M.Sc.
Year: 2020
Subject: Wireless power transmission
Hong Kong Polytechnic University -- Dissertations
Department: Department of Electronic and Information Engineering
Pages: 7, 45 pages : color illustrations
Language: English
Abstract: Wireless power transfer (WPT) technology is becoming more and more popular nowadays. Among WPT technologies, inductive power transfer (IPT) is a world frontier topic in the field of wireless power transmission. IPT mainly uses alternating electromagnetic fields as a mean to transfer energy from a transmitter to a receiver with enough physical separation, similar to an ordinary loosely coupled transformer. Because of this, more and more manufacturers are using IPT technology to achieve wireless charging on their products. This includes the new generation of the Apple pencil. However, the Apple technology is proprietary. The design and internal data of all Apple products are not publicly available. Therefore, it is necessary to redesign a reverse engineered wireless charging stylus based on the current generation of iPad charging mode for the new generation of apple pencil. Theoretically, this thesis compares and studies two different transformers. One of them is a traditional fully coupled transformer, and the other is a loosely coupled transformer. In the analysis of the loosely coupled transformer, two models (mutual inductance model and leakage inductance model) are used. For an efficient power transmission, four basic types of compensation are analysed through circuit theory. The four-basic type of compensations are Series-Series compensation (SS), Series-Parallel (SP) compensation, Parallel-Series (PS) compensation and Parallel-Parallel (PP) compensation. Their basic electrical characteristics are studied in detail. Practically, a PP compensation for a loosely coupled transformer is chosen in this project. The target of the WPT system is to transmit power from a 5 V DC power source through the transmitter of a loosely coupled transformer wirelessly to its receiver which powers an electronic load. An inverter circuit transform the DC power source into a high frequency AC power to drive the primary compensated transformer effectively. The AC power couples efficiently from the transmitter to the receiver of the loosely coupled transformer. The AC power at the receiver is compensated for maximal efficiency and converted using a rectifier circuit to DC power the electronic load. Overall circuit design and implementation are discussed. Eventually, the project is demonstrated experimentally to be operated smoothly. At the same time, optimisation is done from the best result by recording the coupling coefficient and power conversion efficiency at different gap distance. Finally, this thesis also makes a certain outlook on the future development trend of the WPT technology. The improvement for this project by using the optimal design method is mentioned.
Rights: All rights reserved
Access: restricted access

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